Tuesday, 21 August 2012

Guest Blogger - Deborah Sandidge - Long Exposure Photography using Neutral Density Filters

I am blessed to have met some truly inspiring photographers on my own personal photographic journey. This woman in particular is one of those photographers i have been following for the past four years on some of photo sharing websites. Now we are going to be working together. I will get the chance to see her take images and teach others on the workshop and photo tours we will be co-leading... who knows, maybe I will teach her a couple of things as well... LOL
This post of Deb's is exceptional, and discusses one of my favorite types of photography, "long exposure photography with ND filters"... take it away Deb...
Long Exposure Photography using Neutral Density Filters
Copyright Deborah Sandidge
 I was pleased to be able to finally receive the coveted Lee Big Stopper, a 10 stop neutral density filter. It's a challenge to be able to find one in stock, anywhere. You may be able to find a B+W 10 stop, or variable ND which are screw on filters mounting on the lens, compared to Big Stopper which slides in the Lee foundation holder along with any other desired filters. I've used both types of filters, and prefer the stacking slide in type filters. Big Stopper decreases the amount of light entering the camera by 10 stops, giving the photographer the opportunity to control the length of exposure for creative effects. A second neutral density filter, a reverse graduated, can be used to balance light in the sky area. This allows the photographer to work during the daylight hours, rather than the edge of night or day.

Using a 10 stop ND filter is like using an infrared filter, as the filter is too dark to easily see though to focus. To use the filter, compose, meter and a focus first, then mount the filter on the lens (and turn off autofocus). If you have Live View, this will easily allow you to position a graduated ND at the horizon line. A 3 stop reverse neutral density graduated filter holds back brightness at the horizon line and fades towards the top of the filter, this works well for me in most cases. A 10 stop ND filter creates a silky blur with water and softens clouds for an artistic look through the extended exposure time. How much  the clouds blur depends on how fast or slow they move during  the exposure, time. but a cloudless day can be very interesting too.
You can also create a silky blur with water by shooting early morning or late evening, stopping down so that the exposure is long as possible. A polarizer can help with this automatically. If you want to accentuate the look or shoot during the day, neutral density filters can be used to slow down the exposure even more. Anything goes compositionally, however the elements of sky and water fit together for a dramatic image. Exposure time can run into minutes. You'll need...
  • Tripod, and cable release, bulb mode (Nikon MC-36, or similar)
  • Neutral density filters 
  • Timer (I use stopwatch on the iPhone)
  • Exposure calculator (free app, Longtime Exposure Calculator)
  • Close, or cover the eyepiece window 
  • Use Mirror Lock-up, lowest ISO
Meter for the exposure without the filter attached, focus and compose. Turn off autofocus. Calculate the exposure for the neutral density filter, 10 stops, plus the metered exposure time. For example using a 10 stop neutral density filter with a metered exposure time of 1/125 equals 8 seconds with the filter attached. LongTime Exposure Calculator is a handy app and it's free, below is a screenshot. I generally add more time to this, but you get the idea.
I set the white balance to 9000K+ using the Lee Big Stopper for the first image, however this can be tweaked in Photoshop or Lightroom. There is a slight color cast that may occur, and using a custom white balance or dialing in a custom setting seems to do the trick, although a color cast may work for the scene you are shooting. Converting to black and white creates a fine art look that is very expressive without color. 

Long exposures using neutral density filters can capture beautiful color in an image, and convey the passage of time for a surreal and compelling photograph. This gives the photographer more options during the day for an alternative type of composition. Have fun shooting! ~ Deb
To see the whole post with some more amazing images please visit Deb's blog here
To check out the first workshop Deb and I will be leading together, please visit http://www.photographers-lounge.com/photo-tours/our-2013-photo-tours/mongolia-photo-tour/